Some fear that the total yield to the Revenue from the reforms could be as high as £10bn, a figure that dwarfs the Treasury’s estimate of £100m.

However, few accountants were this morning supporting £10bn headline estimate from PricewaterhouseCoopers, prefering to reserve judgement or guess at figures of £1bn or £2bn.

Stephen Barrett, head of tax consulting at Ernst & Young, said: ‘It’s at least £1bn, and probably significantly more than that.’

Joyce Svasti-Salee, head of international tax at KPMG, said at least one multi national had estimated the increase in its tax liability at 4-5%. She said: ‘We are making some sort of estimate at the moment because we think the £100m is generally understated.’

The Treasury is quoted in the Financial Times as standing by its figures and claiming ‘the costing is robust’.

The government is reported to argue that the PwC £10bn estimate is based on a ‘misunderstanding’.

Further fury is growing among accountancy firms over the way Double Tax Relief reform has come about.

The government announced consultation on the subject in April 1998 and promised responses from interest parties would be made public. However, Stephen Barret at E & Y said only a ‘stony silence’ had followed the end of the consultation.’Those responses have not been made available. We would like to see those responses made available as promised.’